Optical devices generally include one or more cladding layers around optical waveguides to confine their optical modes. An example of a cladding layer is a buried oxide (BOX) layer on a silicon on insulator (SOI) wafer. Cladding layers are generally made from materials with low thermal conductivity. Low thermal conductivity cladding layers may cause thermal dissipation problems for active devices such as amplifiers and photodetectors.
Some current implementations attempt to solve thermal dissipation problems with polysilicon shunts in the buried oxide layer; however, polysilicon shunts in the buried oxide layer have drawbacks. For example, polysilicon shunts are wide, and thus provide a radiation path for the optical mode. Therefore, current implementations require placement of polysilicon shunts a certain lateral distance away from the optical mode. The effectiveness of such polysilicon shunts is greatly reduced because the shunts are located far from the active region of the device where heat dissipation is greatest.
Additionally, polysilicon has a low thermal conductivity (between three to ten times lower than crystalline silicon) and therefore thermal performance improvements due to polysilicon shunts as currently implemented are marginal.
Descriptions of certain details and implementations follow, including a description of the figures, which may depict some or all of the embodiments described below, as well as discussing other potential embodiments or implementations of the inventive concepts presented herein. An overview of embodiments of the invention is provided below, followed by a more detailed description with reference to the drawings.